1. Field
This disclosure relates generally to semiconductors, and more specifically, to the security and functional use of semiconductors.
2. Related Art
Integrated circuits commonly use data elements that must be kept secret from unauthorized third parties. For example, banking cards should be maintained with the highest security available. The secret data elements are commonly contained in programmable non-volatile memories such as EEPROMs, EPROMs or flash EPROM. For these types of memories it is vital to prevent access to these data elements in all circumstances. Conventional techniques used to protect data elements of an integrated circuit include the use of encoding mask circuits, access protection circuits and secured software procedures for protecting access to the secure data elements.
Another technique which has been proposed to protect sensitive information in an integrated circuit is to render the integrated circuit useless should various forms of tampering be detected. Such forms include abnormal variation in ambient temperature, changes in the luminosity such as may occur from the depassivation of the integrated circuit, an abnormal level of a supply voltage, multiple abortive read or write attempts and others.
A type of semiconductor memories is known as Magnetoresistive Random Access Memory or MRAM. MRAM devices operate using magnetic tunnel junction devices. MRAM stores data as a magnetic state, rather than charge, and is sensed by measuring the resistance without disturbing the magnetic state. However, finding methods and circuitry to protect the security of data elements stored in MRAM devices is as problematic as with programmable non-volatile memories.